Novel Anti-Reflection Technology for GaAs Single-Junction Solar Cells Using Surface Patterning and Au Nanoparticles

Kim, Youngjo,Lam, Nguyen Dinh,Kim, Kangho,Kim, Sangin,Rotermund, Fabian,Lim, Hanjo,Lee, Jaejin American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7

<P>Single-junction GaAs solar cell structures were grown by low-pressure MOCVD on GaAs (100) substrates. Micro-rod arrays with diameters of 2 microm, 5 microm, and 10 microm were fabricated on the surfaces of the GaAs solar cells via photolithography and wet chemical etching. The patterned surfaces were coated with Au nanoparticles using an Au colloidal solution. Characteristics of the GaAs solar cells with and without the micro-rod arrays and Au nanoparticles were investigated. The short-circuit current density of the GaAs solar cell with 2 microm rod arrays and Au nanoparticles increased up to 34.9% compared to that of the reference cell without micro-rod arrays and Au nanoparticles. The conversion efficiency of the GaAs solar cell that was coated with Au nanoparticles on the patterned surface with micro-rod arrays can be improved from 14.1% to 19.9% under 1 sun AM 1.5G illumination. These results show that micro-rod arrays and Au nanoparticle coating can be applied together in surface patterning to achieve a novel cost-effective anti-reflection technology.</P>

Computational design of one-dimensional nonlinear photonic crystals with material dispersion for efficient second-harmonic generation

Kim, Sangbum,Kim, Kihong,Rotermund, Fabian,Lim, Hanjo The Optical Society 2009 Optics express Vol.17 No.21

<P>A computational study of the second-harmonic generation in one-dimensional photonic crystals made of GaAs and AlAs with quadratic optical nonlinearity and material dispersion is presented. The computational approach uses a shooting method to solve nonlinear wave equations for coupled fundamental and second-harmonic fields and the invariant imbedding method to obtain the linear transmittance and group index spectra. The photonic crystal is built with an elementary cell consisting of four sublayers whose thicknesses are systematically varied. Doubly-resonant second harmonic generation with high conversion efficiency is achieved by choosing the geometrical parameters of the elementary cell optimally and controlling the band structure.</P>

Proposal for ideal 3-dB splitters-combiners in photonic crystals.

Kim, Sangin,Park, Ikmo,Lim, Hanjo Optical Society of America 2005 Optics letters Vol.30 No.3

<P>We propose a structure for ideal 3-dB splitters (1 x 2)-combiners (2 x 1) in photonic crystals. In photonic crystals, ideal 3-dB splitters based on a three-port system are achievable in principle, but it is impossible to achieve ideal 3-dB combiners based on the three-port system because there is no path for a loss, owing to strong confinement of photons. The proposed structure is based on a four-port system in which the concept of a microwave circuit, the so-called rat-race circuit is adopted. Design conditions for two-dimensional photonic-crystal-based rat-race circuits have been investigated by use of the coupled-mode theory in time. With the proposed structure, a 3-dB splitter-combiner has been designed. The performance of the device was numerically calculated by the finite-difference time-domain method.</P>

Ab-initio Study for the Correlation Effect on the Magneto-optical properties of Co-based Full Heusler Alloys

Miyoung Kim,Tran Van Quang,Hanjo Lim,Jae Il Lee 한국자기학회 2010 한국자기학회 학술연구발표회 논문개요집 Vol.2010 No.12

웨어러블 디바이스를 이용한 반려동물 원격 모니터링 시스템

정한조(Hanjo Jeong),이정훈(Jeong-Hun Lee),이지형(Ji-Hyeong Lee),김세윤(Se-Yun Kim),정지원(Ji-Won Jung) 한국컴퓨터정보학회 2020 한국컴퓨터정보학회 학술발표논문집 Vol.28 No.2

Invariant Imbedding Theory of Wave Propagation in Stratified Complex Media

Kihong Kim,Hanjo Lim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

We review a generalized version of the invariant imbedding theory of wave propagation, which has been developed by us recently, in various kinds of stratified media. The main idea of the method is to transform the boundary value problem of the original wave equation into an equivalent initial value problem of coupled ordinary dierential equations. This allows an exact and very efficient numerical calculation of the re ection and the transmission coefficients and of the wave functions inside inhomogeneous media. We demonstrate the advantages of the method over other theoretical methods by applying it to several interesting cases. In the rst case, we apply the method to the propagation of electromagnetic waves in random dielectric media. Next, we give a short discussion of the application of our method to wave propagation in nonlinear inhomogeneous media. Finally, we discuss the generalization of the invariant imbedding method to cases where several coupled waves propagate in arbitrarily-inhomogeneous stratied media and apply it to electromagnetic wave propagation in layered chiral media. We review a generalized version of the invariant imbedding theory of wave propagation, which has been developed by us recently, in various kinds of stratified media. The main idea of the method is to transform the boundary value problem of the original wave equation into an equivalent initial value problem of coupled ordinary dierential equations. This allows an exact and very efficient numerical calculation of the re ection and the transmission coefficients and of the wave functions inside inhomogeneous media. We demonstrate the advantages of the method over other theoretical methods by applying it to several interesting cases. In the rst case, we apply the method to the propagation of electromagnetic waves in random dielectric media. Next, we give a short discussion of the application of our method to wave propagation in nonlinear inhomogeneous media. Finally, we discuss the generalization of the invariant imbedding method to cases where several coupled waves propagate in arbitrarily-inhomogeneous stratied media and apply it to electromagnetic wave propagation in layered chiral media.

Bayesian Model for the Classification of GPCR Agonists and Antagonists

Inhee Choi,Hanjo Kim,Jihoon Jung,남기엽,유성은,강남숙,노경태 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.8

G-protein coupled receptors (GPCRs) are involved in a wide variety of physiological processes and are known to be targets for nearly 50% of drugs. The various functions of GPCRs are affected by their cognate ligands which are mainly classified as agonists and antagonists. The purpose of this study is to develop a Bayesian classification model,that can predict a compound as either human GPCR agonist or antagonist. Total 6627 compounds experimentally determined as either GPCR agonists or antagonists covering all the classes of GPCRs were gathered to comprise the dataset. This model distinguishes GPCR agonists from GPCR antagonists by using chemical fingerprint, FCFP_6. The model revealed distinctive structural characteristics between agonistic and antagonistic compounds: in general, 1)GPCR agonists were flexible and had aliphatic amines, and 2) GPCR antagonists had planar groups and aromatic amines. This model showed very good discriminative ability in general, with pretty good discriminant statistics for the training set (accuracy: 90.1%) and a good predictive ability for the test set (accuracy: 89.2%). Also, receiver operating characteristic (ROC) plot showed the area under the curve (AUC) to be 0.957, and Matthew’s Correlation Coefficient (MCC) value was 0.803. The quality of our model suggests that it could aid to classify the compounds as either GPCR agonists or antagonists, especially in the early stages of the drug discovery process.

Improved bending loss characteristics of asymmetric surface plasmonic waveguides for flexible optical wiring

Lee, Sangjun,Kim, Sangin,Lim, Hanjo The Optical Society 2009 Optics express Vol.17 No.22

<P>We present improved characteristics of the curved plasmonic waveguide which consists of a thin metal stripe with asymmetric cladding layers. It is shown that in the proposed curved asymmetric plasmonic waveguides, a balance between a radiation due to bending and a radiation due to the asymmetric claddings allows a bending with a smaller radius curvature and a lower loss compared to the waveguide with symmetric claddings. At the same time, a symmetric metal stripe waveguide's typical trade-off between the bending characteristics and the propagation loss of a straight waveguide is relaxed with proper amount of asymmetry. With the proposed structure, a plasmonic waveguide bending whose radius is as small as 2 mm with a total loss of 1.8 dB/90 degrees is designed. Enhanced sensitivity to the surrounding medium and its application are discussed.</P>

Higher order optical resonant filters based on coupled defect resonators in photonic crystals

Park, Dongsoo,Kim, Sangin,Park, Ikmo,Lim, Hanjo IEEE 2005 Journal of Lightwave Technology Vol.23 No.5

In this paper, a general methodology for the design of higher order coupled resonator filters in photonic crystals (PCs) is presented. In the proposed approach, the coupling between resonators is treated as though it occurs through a waveguide with an arbitrary phase shift. The coupling through the waveguide is analyzed theoretically, based on the coupled-mode theory in time. The derived theoretical model suggests a way to extend an equivalent circuit approach, previously demonstrated with a certain value of a phase shift, to the higher order filter design with an arbitrary phase shift. The validity of the proposed approach is confirmed by the design of a third-order Chebyshev filter having a center frequency of 193.55 THz, a flat bandwidth of 50 GHz, and ripples of 0.3 dB in the passband. The characteristics of the designed filter are suitable for wavelength-division-multiplexed (WDM) optical communication systems with a 100-GHz channel spacing. The performance of the designed filter is numerically calculated using the two-dimensional (2-D) finite-difference time-domain (FDTD) method.

Aerosol delivery of urocanic acid-modified chitosan/programmed cell death 4 complex regulated apoptosis, cell cycle, and angiogenesis in lungs of K-ras null mice.

Jin, Hua,Kim, Tae Hee,Hwang, Soon-Kyung,Chang, Seung-Hee,Kim, Hyun Woo,Anderson, Hanjo K,Lee, Han-Woong,Lee, Kee-Ho,Colburn, Nancy H,Yang, Hsin-Sheng,Cho, Myung-Haing,Cho, Chong Su American Association for Cancer Research, Inc 2006 Molecular cancer therapeutics Vol.5 No.4

<P>The low efficiency of conventional therapies in achieving long-term survival of patients with lung cancer calls for development of novel treatment options. Although several genes have been investigated for their antitumor activities through gene delivery, problems surrounding the methods used, such as efficiency, specificity, and toxicity, hinder application of such therapies in clinical settings. Aerosol gene delivery as nonviral and noninvasive method for gene therapy may provide an alternative for a safer and more effective treatment for lung cancer. In this study, imidazole ring-containing urocanic acid-modified chitosan (UAC) designed in previous study was used as a gene carrier. The efficiency of UAC carrier in lungs was confirmed, and the potential effects of the programmed cell death protein 4 (PDCD4) tumor suppressor gene on three major pathways (apoptosis, cell cycle, and angiogenesis) were evaluated. Aerosol containing UAC/PDCD4 complexes was delivered into K-ras null lung cancer model mice through the nose-only inhalation system developed by our group. Delivered UAC/PDCD4 complex facilitated apoptosis, inhibited pathways important for cell proliferation, and efficiently suppressed pathways important for tumor angiogenesis. In summary, results obtained by Western blot analysis, immunohistochemistry, and terminal deoxynucleotidyl transferase-mediated nick end labeling assay suggest that our aerosol gene delivery technique is compatible with in vivo gene delivery and can be applied as a noninvasive gene therapy.</P>